It is desirable to transmit data along a line without the need for wires or radio frequency (electromagnetic) communications devices. Examples abound where the installation of wires is either technically difficult or economically impractical. The use of radio transmission may also be impractical or unavailable in cases where radio-activated blasting is occurring, or where the attenuation of radio waves near the line is significant.
Likewise, it is desirable to collect and transmit data along a line in a wellbore, such as during a drilling process, or in the offshore applications—i.e. mooring lines, risers, etc. Such data may include temperature, pressure, inclination, azimuth, fluid composition, optical images, and localized motion and rotation of the line. These data are used to facilitate monitoring integrity of a line in real time, monitor deformation along the line, and monitor stress and corrosion at specific points along the line, hull cracking, coating degradation, and leakage, among other things.
Currently, such data is collected via a multiplicity of systems and methods with limited detection capabilities. Deployed load sensors can monitor the overall tension, e.g., in a mooring line, but cannot identify damages caused by localized erosion/corrosion, and thus, cannot accurately predict failures. Inclinometers at the surface of the water may not detect failures of a line in real time, especially in catenary mooring systems. Moreover, even though inclinometers can offer a reliable warning of mooring line failure, the conversion of angles into tensions must still be done using estimated lookup tables, resulting in lost accuracy in tension measurements. Sonar/Video mapping can also be used to provide data associated with the health of a line, but such measurements are expensive and are currently done with Remote Operated Vehicles (ROVs)—that is, the data is acquired as needed and cannot provide real-time information, such as information related to the trenching conditions due to the movement of a mooring line close to the sea bottom. Optical fiber based shape sensing systems have been deployed along various lines, but are difficult to implement in offshore applications due to the large deformation and dynamic movements of the lines tend to damage the optical fibers. Strain gauges have been implemented to monitor lines, such as risers, but only monitor the localized conditions and do not monitor the overall health of the line.
Several real time data telemetry systems have also been offered. One involves the use of a physical cable such as an electrical conductor or a fiber optic cable that is secured to the line. The cable may be secured to either the inner or the outer diameter of the pipe. The cable provides a hard wire connection that allows for real-time transmission of data and the immediate evaluation of subsurface conditions. Further, these cables allow for high data transmission rates and the delivery of electrical power directly to downhole sensors.
The use of acoustic telemetry has also been suggested. Acoustic telemetry employs an acoustic signal generated at or near the bottom of the line. The signal is transmitted through a wellbore pipe or water, meaning that the pipe or water becomes the carrier medium for sound waves. Transmitted sound waves are detected by a receiver and converted to electrical signals for analysis.
U.S. Pat. No. 5,924,499 entitled “Acoustic Data Link and Formation Property Sensor for Downhole MWD System” teaches the use of acoustic signals for “short hopping” a component along a drill string. Signals are transmitted from the drill bit or from a near-bit sub and across the mud motors. This may be done by sending separate acoustic signals simultaneously—one that is sent through the drill string, a second that is sent through the drilling mud, and optionally, a third that is sent through the formation. These signals are then processed to extract readable signals.
U.S. Pat. No. 6,912,177, entitled “Transmission of Data in Boreholes,” addresses the use of an acoustic transmitter that is part of a downhole tool. Here, the transmitter is provided adjacent a downhole obstruction such as a shut-in valve along a drill stem so that an electrical signal may be sent across the drill stem. U.S. Pat. No. 6,899,178, entitled “Method and System for Wireless Communications for Downhole Applications,” describes the use of a “wireless tool transceiver” that utilizes acoustic signaling. Here, an acoustic transceiver is in a dedicated line that is integral with a gauge and/or sensor. This is described as part of a well completion.
Faster data transmission rates with some level of clarity have been accomplished using electromagnetic (EM) telemetry. EM telemetry employs electromagnetic waves, or alternating current magnetic fields, to “jump” across pipe joints. In practice, a specially-milled drill pipe is provided that has a conductor wire machined along an inner diameter. The conductor wire transmits signals to an induction coil at the end of the pipe. The induction coil, in turn, then transmits an EM signal to another induction coil, which sends that signal through the conductor wire in the next pipe. Thus, each threaded connection provides a pair of specially milled pipe ends for EM communication.
National Oilwell Varco® of Houston, Tex. offers a drill pipe network, referred to as IntelliServ®, that uses EM telemetry. The IntelliServ® system employs drill pipe having integral wires that can transmit LWD/MWD data to the surface at speeds of up to 1 Mbps. This creates a communications system from the drill string itself. The IntelliServ® communications system uses an induction coil built into both the threaded box and pin ends of each drill pipe so that data may be transmitted across each connection. Examples of IntelliServe® patents are U.S. Pat. No. 7,277,026 entitled “Downhole Component With Multiple Transmission Elements,” and U.S. Pat. No. 6,670,880 entitled “Downhole Data Transmission System.”
It is observed that the induction coils in an EM telemetry system must be precisely located in the box and pin ends of the joints of the drill string to ensure reliable data transfer. For a long (e.g., 20,000 foot) well, there can be more than 600 tool joints. The represents over 600 pipe sections to be threadedly connected. Further, each threaded connection is preferably tested at the drilling platform to ensure proper functioning.
National Oilwell Varco° promotes its IntelliServe® system as providing the oil and gas industry's “only high-speed, high-volume, high-definition, bi-directional broadband data transmission system that enables downhole conditions to be measured, evaluated, monitored and actuated in real time.” However, the IntelliServe® system generally requires the use of booster assemblies along the drill string. These can be three to six foot sub joints having a diameter greater than the drill pipe placed in the drill string. The booster assemblies, referred to sometimes as “signal repeaters,” are located along the drill pipe about every 1,500 feet. The need for repeaters coupled with the need for specially-milled pipe can make the IntelliServe® system a very expensive option.
Recently, the use of radiofrequency signals has been suggested. This is offered in U.S. Pat. No. 8,242,928 entitled “Reliable Downhole Data Transmission System.” This patent suggests the use of electrodes placed in the pin and box ends of pipe joints. The electrodes are tuned to receive RF signals that are transmitted along the pipe joints having a conductor material placed there along, with the conductor material being protected by a special insulative coating.
While high data transmission rates can be accomplished using RF signals in a downhole environment, the transmission range is typically limited to a few meters. This, in turn, requires the use of numerous repeaters.
Chinese Pat. No. CN102385051 entitled “Device and Method for Monitoring Mooring System Based on Short Base Line Hydro-Acoustic Positioning” describes a direct acoustic positioning system. Multiple acoustic signal interrogators and transponders are positioned at the bottom of a floating platform, seabed, and along an anchor chain. The monitoring system performs real-time online measuring and monitoring of the shape of a mooring line, but relies solely on ultrasonic wave propagation under water, which diminishes its accuracy.
WO App. No. 2013/154231 entitled “Method and System for Static and Dynamic Positioning of Marine Structure by Using Real-Time Monitoring of Mooring Line” describes the use of optical fibers to monitor the strain of the various mooring lines attached to the marine structure and converts the strain measurements into an approximation of location of the marine structure. As described above, optical fibers can be easily damaged based on large deformations that can occure in mooring lines.
Addtionally, several articles have been written regarding mooring line integrity as well as riser monitoring. Steven et al., in Mooring Line Monitoring to Reduce Risk of Line Failure, describes a system using inclinometers to measure the mooring system condition and inform on the effective loading of each anchor leg. Proceedings of the International Offshore and Polar Engineering Conference, 388-93 (2014). The system determines average line tension using estimated lookup tables based on data transmitted acoustically to a surface control room. Angus, in Real Time 24/7 Integrity Monitoring of Mooring Lines, Risers, and Umbilicals on a FPSO Using 360 Degree Multibeam Sonar Technology, invokes multibeam sonar scanning to monitor the bend of the mooring line. SPE Offshore Europe Conference and Exhibition, 646-56 (2013). This is not a direct measurement of the mooring line and can be affected by environmental conditions. Blondeau et al., in Riser Integrity Monitoring for Offshore Fields, describes a vibrating wire gauge utilized as a strain gauge to monitor the integrity of risers and riser towers. Offshore Technology Conference (Asia) (Mar. 25, 2014-Mar. 28, 2014).
Accordingly, a need exists for a low cost, low maintenance, reliable system and method for monitoring lines. The present disclosure provides a monitoring system utilizing an ultrasonic wireless communication network and various sensors to assess the overall heath of the line. All measurement devices are embedded within the sensors and data fusion techniques can be used to develop an overall health assessment of the line.